The invention relates to a pump having a cutting wheel and a pre-cutter driven by a shaft portion that projects axially from the cutting wheel and has a plurality of wings that extend radially from the shaft portion.
A pump of this type is known from DE 10 2008 031 842 B3 and is used for example in machine tools for circulating lubricating coolant emulsions that are contaminated with metal chippings. This pump is a centrifugal pump that has, in addition to a radial impeller, an axial impeller disposed upstream of the radial impeller, said axial impeller being configured as a cutting impeller and having, at its upstream end, cutting edges that cooperate with stationary counter blades arranged radially in a suction passage, so that chippings and other contaminants that have been sucked in are cut-off and chopped. The pre-cutter serves for chopping coarse contaminants before they are sucked-in by the axial impeller and are then chopped further.
U.S. Pat. No. 6,224,331 B1 and U.S. Pat. No. 5,460,483 show pumps with similar pre-cutters.
In a typical installation scenario, the pump is disposed vertically in a collecting vessel for the liquid coolant, so that the pre-cutter is disposed at a certain vertical distance from the bottom of the vessel. The wings of the pre-cutter are inclined relative to the plane of rotation of the wings, similarly as in a propeller, so that the chippings can be sucked-in and conveyed better.